Intercept discriminator



`Ian. 27, 1959 H. L. HORWITZ ET AL INTERCEPT DISCRIMINATOR 2 Sheets-Sheet 1 Filed March y12. 1953 Jam 27, 1959 H. l.. HoRwlTz ET AL 2,871,300

INTERCEPT DISCRIMINATOR 2 Sheets--Sheev 2 Filed March 1 2, 1955 United StatesI Patent y 2,871,300 INTERCEPT DISCRIMINATOR Henry Leopold Horwitz, Nutley, and George Louis Hasser, Packanack Lake, N. J., assignors to International VTelephone and Telegraph Corporation, a corporation of Maryland pplication 12, 1953, Serial No. 341,856

13 Claims. (.Cl. 179-27) This invention relates to telephone systems and more r systems,`when one or more of the sub-stations associated with a multiparty subscribers line is'taken out of service or disconnected from the line, it is desirable tov provide an arrangement whereby calls intended/for the disconnected sub-station are routed to an intercepting trunk so that thecalling subscriber can be informed that the called sub-station is no longer in service.

It is one .object of the present invention to provide improved circuits of the character described, which are simple and economical and which function in a positive applying ground to the sleeve terminal of .the called and reliable manner to intercept 4calls to one or more predetermined sub-stations on party lines, andto extend automatically the intercepted calls to a common intercept trunk in order that the calling party may be informed that the called station is out of service.

Another object of our invention is to provide'an improved method of identifying intercepted calls on multiparty lines. f

According to one feature of our invention afnintercept discriminator to which a' called party line with one or vmore out. of. service' stations is extended, comprises aI set oftest relays adapted to respond selectively to char- 'A acteristic ringing currents applied to theline and a chain of further `relays which connect up in sequential yorder only those test relays which correspond to out of service stations, calls to out of service stations being extended l to an intercept trunlcunder the control of the test relays. Other objects', purposes and characteristic features of our invention Will 'be apparent fromy a studyof'the ac companying drawingsv inconjunction with the following description;

Since the invention is concerned primarily with the Viinal selector stage of an automatic telephone switching system, only those parts of suchia system are shown as are required to understand a preferred method of`practicing the invention.

v In the-drawings: n L i, Fig. l represents in a schematic fo` the circuits used in establishing an intercept call including parts of fa connector, a subscribers line, an ladapter for the subscribers -tended to the intercept trunk, and vfor all other calls disconnects the discriminator and concentration circuit.

While certain features of the invention are broadly `applicable toany type of party line telephone system, it

will ybe' assumed that the, invention is ,applied to a party "line telephone systeml in which several .different frequentransfers the connection to anf intercept trunk.

cies areemployed for selectively ringing the bells on a selected party line. It is also assumed that the lines in the particular system to which this invention is applied are divided circuitringing lines, with several stations selected byringing over one side ofthe lineto ground andy with several additional stations selected by ringing over Vthe other side of the line to ground.

it is believed lthat the invention will be best understood b y explaining the operation when a connection is made to the linecircuit illustrated in vFigure l, assuming that Ya ringing current of a particular frequency is 'applied to the line, that -thestation which responds to this frequency has been disconnected, and that the call should be routed to an'intercept trunk in order that the calling subscriber maybe informed that the called station is out of service. v

Figure l shows a portion of a connector of a type Well known in the art and comprising a cut-through relay C1, a ringing relay R1,` a reversing `relay RV, a trip relay TR', a frequency selecting minor switch FS and connector wipers TL, RL andSL. It will be understood that the connection from the calling line to thecalled lineis made inthe usual manner through the connector by way of thetip line wiper TL and the ring line wiper RL, withA the sleeve line wiper SL of the connector line circuit for-making this line'busy and for' operating the,1 cut-off relay.V After the. called line is selected, it 1s usually the practice to dial a station selecting digit which operatesl the frequency selecting sWitch..,FS to select the lproper `frequency for ringing the desired station. Fur

thermore, the reversing relay RV, associated with the connector, may be left in its normalposition for ringing over the'. tip side ,of the line or it may be operated for ringing over the ring side" of the, line. YIt is also well known by'those skilled in they art how cut-in relay C1 is operated 'after the line is' selected,` how ringing relay R1 is operated to ring the called line and lhow ytrip relay VTR isoperated for releasing R1 to disconnect theline fronithe ringing circuit and for connectingit through to the'talking circuit, including" the calling line.

' Thejcoricentration circuit, a part of which is illustrate in Figure l, is well known to those skilled in the artand comprises a start relay ST, a'cut-through relay CT, a transfer relayI TK and a finder switch. VIt will beunderstood that the nder switch operates in well-known manner` to" extend connections from subscribersf lines requir- 'ing'r intercept services to a discriminator and intercept trunk. The start relay ST causes the inder switch toy'.

engage aycalling line adapter circuit, relay CT extends the connection to the discriminator circuit and relay TK The discriminatorfcircuit is shown in a ksim lined feria in Figure 2.A Two sets of relays and C A-` CX are provided for the purposel of comparing the frequency of the' ringing current transmitted with the `frequency to be intercepted. Relays FRA-PRX are each responsive to a p a'rticularringing frequency and when operatedindicate'that a call/shall be intercepted.; yOne or more oftheserelays will be connected to a subscribers line, in'` a sequentialorder,"by means of the cascade relays lCA--VCX, which in turn are controlled by jumper- -ing on the cross connecting frame XC. `When astation is to be intercepted the 4circuits ywill be prepared asfollows: An adapter circuit will be connected -to a subscribers line to be intercepted, by means of conductors 15,4 16k and'17, and-jurnper-wires will be provided'between intercepted. It will be understood thata set -of termlnals such as 91-96 will be provided for each position of the concentration nder, corresponding terminals of each set being connected incommon to the contacts 58, 59 and 60 of the relay DT. These terminals 9--96 are further dividedkinto two groups, namely, odd terminals 91, 93, 95 for stations signalled via tip conductor 15 of the line and even terminals 92, 94, 96 for stations signalled via the ring conductor` 16. The detailed circuit operation takesplace as described presently. lt may be noted that only those relays and connections are shown which are required to illustrate the'invention. it is to be understood that in practice equipment will be supplied in accordance with the maximum numbers of stations provided Vfor multi-party lines,

It will now be assumed that the line circuit illustrated 'in Figure l has been selected, that ringing current of a particular frequency is selected and that the station responsive to this frequency has been disconnected. Fun

ther, that the subscribers line is connected to an adapter circuit which in turn is connected to a set of vterminals on the finder switch of the concentration circuit. When ground is applied to the sleeve terminal in the connector a circuit is closed for relay A via contacts 11 of relay B of the adapter circuit, resistance 12, rectifier 13, Windlthe discriminator the T and R leads ofthe line. circuit.

A circuit is further completed for relay DA (Fig. 2)

from ground, contacts 21, 29, conductor 35, winding of relay DA to battery. Y v

Relay DA operates and causes the operation of relay CA via a circuit which may be traced from ground, contacts 42 of DA, contacts `46 of DR, ycontacts 56 of DT, winding of CA to battery. CA is the rst of a chain of relays connected in cascade and terminated by relays CX and CY. When' CA operates, a circuit is completed for the succeeding relay in the series, thus causing the successive operationof the whole series. The operating circuit of the last relay illustrates theV method of operation and may be traced from ground contacts 43 of DA, contacts 73 of CX, winding of CY to battery.

When relay CY operates, the T and R conductors are extended at contacts 75 and 76 from the connector to relays RT and RR. One of these circuits may be traced from ground, condenser 80, windings of relay RT, rectiers 81, contacts 75 of CY, conductor 31, contacts 26 of 'TK, contacts 22 of CT, Wiper FT Wiper TL Contacts of relays C1, R1, RV to ground or to the ringing current supply via winding of TR, frequency selecting switch FS, lamp 15, and secondary winding 16 of ringing transformer to battery. The other circuit via the vR conductor may be traced from ground, condenser 82, windings of relay RR', rectiers 83, contacts 76 of CY, conductor 32, contacts 27 of TK, contacts 23 of CT,.wiper FR, wiper RL, contacts of C1, R1, RV to ground or to the ringing current supply over the circuit previously traced.

Relays RR and RT operate alternatively on any frequency of ringing current to indicate to the discriminator the particular talking wire over which the called party is being signalled. Assume that ringing current is transmitted over the T conductor; relay RT will operate and cause the operation of relay DT, via a circuit closed from ground contacts 41, contacts 52, winding of DT to battery. Relay DT locks via contacts 55 and prepares via contacts 58--60'a circuit for checking whether or not the call shall be intercepted. Relay DT also opens the circuit for the rst cascade relay CA, which releases and in turn causes the release one after another of the other slow releasing cascade relays. Each cascade relay Aupon releasing prepares at'contacts tid-71a circuit for 4 an A. C. relay FRA- PRX tuned to a particular ringing frequency. The cascade relays CA-CX also prepare via contacts 69-74 a circuit for checking or comparing a particular frequency or substation in a manner which will now be described.

As an example of the circuit operation, assume that calls to a particular party on the subscriber line are required to be intercepted. Assume further that this party is signalled via the T conductor ofthe party line, and by the particular ringing frequency to which A. C. reiay FRX responds. To indicate that calls to the particular party are to be intercepted, a connection has been made between terminals "and 95 on the cross connection terminal frame XC.

Now when a ringing current is transmitted via the T conductor, relays RT and DT operate and the cascade relaysk CA--CX, CY release one after another, as previously described. When CX closes its back contacts 74 a circuit is completed for relay D. C. from ground Via contacts 57 of DT, 64 of DS, 74 of CX, 60 of DT,

` completes a circuit for. the transfer relay TK in the concentration circuit.y This ycircuit may be traced from ground via contacts '70 of FRX,r conductor 53, upper winding of TK to battery. Relay TK operates and locks over its lower winding via its contacts 28 and contacts 25 of CT. TK opens at contactsA 29 the circuit forrelay DA, which in turn causes the release of all relays in the discriminator circuit. Relay TK also transferstheT and R conductors of the line to the intercept trunk, which may be of any type Well known to the art. The call may be terminated at an operators position or a tone may be transmitted, thus informing the calling subscriber that the called party is out of service.

When the calling subscriber releases, ground is removed from the S conductor of the-line circuit which in turn fcauses the release of all relays in the concentration circuit. .i j

Whencalls are made to other parties on the line, which areV not to be intercepted, the ringing current will be 'of a frequency to which A. C. relay FRX does not respond. Thus all they cascade relays release and' relay CY upon releasing icompletes a circuit for relay B in the adapter circuit, from ground via contacts 77 of CY, 54

-of DT (or 44 of DR), conductor 34, Wiper FS of the concentration finder switch, lower winding of' relay B to battery. Relay B locks via contacts 11 to the grounded S conductor of the line andv also opens at contacts 11 the circuit of relay CT which in turn causes the release of the discriminator circuit.

When the party to be intercepted is signalled via the R conductor, the circuit operation takes place in a similar manner but relays RR and DR operate. in place of 'RTvand DT. Further, the circuit for operating relay Aintercepted, jumpering will be provided for the ringing frequency of each party, and further a rectier or other form of uni-directional conducting devicewill be inserted in every jumper wire, so as to prevent interference by -other partyA lines.

92', 94 and rectifers 97' illustratesthe The jumpering' between terminals 85, jumpering required for' the interception of two parties.A

The ringing frequencies are checked during the time ringing current is transmitted from the connectors and when the ringing current is interrupted the cascade relays CA'-CX, which happen to be operated, are prevented from releasing in the following manner: When the ringing current is interrupted, relay RT (or RR) releases thereby completing a circuit for Arelay DS from ground via contacts 47 of DR (or S7 of DT), 50 of RR, 53 of RT, winding of DS to battery. Relay DS at contacts 61, 62, 63 supplies a locking ground from contacts 43 to the cascade relays in the same Way as illustrated for relays CA, CX and CY. When ringing is again transmitted RT (or RR) operates and DS releases thus `causing the circuit to function as previously explained., A

If a call is made to a party not requiring intercept service, the party may answer while the intercepting circuits are connected to the called line. In this case relay B of the adapter circuit will be operated over the subscribers line. Relay B locks to a ground supplied from a connector via the S conductor and short circuits its upper operating winding in order to reduce transmission loss in the talking circuit. Moreover, the circuit for relay CT is opened at contacts 11, thus causing the release of the common intercept circuits. v

On calls originated on a multi-party line, relay B operates inseries with the usual line relay and locks via the S conductor to the succeeding equipment. Relay B opens the circuit for the starting relay A thus preventing the functioning of the common intercept circuitsfon incoming calls.

While we have described our preferred embodiment of our invention it is to be understood that various modifications and changes may be applied to meet the requirements of practice without departing from the spirit or Vscope of our invention as claimed in the appended claims.

What is claimed is:

l. An intercept system for telephone party lines comprising means for selectively signalling stations on said lines, an intercept discriminator, means for extending a called party line to said discriminator, a set of test relays in said discriminator adapted to respond selectively to selective ringing currents, means for connecting one terminal of said test relays to said line and a chain of further relays in said discriminator for completing in sequential order the circuits of only those test relays which correspond to stations out of service.

2. An intercept system for telephone party lines comprising means for applying selective ringing currents of different frequency to said lines, an intercept discriminator, means for extending a called party line to said discriminator, a set of tuned relays in said discriminator adapted to respond selectively to said selective ringing currents of different frequencies, means for `connect-mg one terminal of said tuned relays to said line, a chain of further relays in said discriminator for completing in sequential order the circuits of only those tuned relays which correspond to stations out of service, an .intercept trunk, and means under the control of said tuned relays for extending the connection to said intercept trunk.

3. An intercept system for telephone party lines comprising means for applying selective ringing currents of diiferent frequency to said lines, an intercept discriminator, a finder for extending a called party line to said discriminator, a set of tuned relays in said discrimmator adapted to respond selectively to said selective ringing currents of different frequencies, means for connecting one terminal of said tuned relays to said line, a chain of further relays in said discriminator, means for energizing in succession the relays of said chain when said called party line is extended to said discriminator, means responsive to the application of ringing current to said line for initiating the successive deenergization of the relays ofsaid chain, and 4means controlled by said finder and by the deenerg-ization of the relays of said chain of further relays for completing only those circuits of the tuned relays which correspond to out of service stations.

4. An intercept system, according to claim 3, further comprising an intercept trunk and a further relay for transferring said party line from said discriminator to said intercept trunk, and circuits for said further relay including contacts of said tuned relays.

5. In an automatic telephone lswitching system, party lines, means for extending connections to said party lines, an intercept discriminator, a finder switch for extending a connection from a called party line to said discriminator when a call is made to a party line, means for applying ringing currents of diierent frequency to said party line, a first set of tuned relays in said discriminatorl adapted to respond selectively to said ringing currents of different frequency, means for connecting one terminal of said tuned relays to said line, a second set of relays in said discriminator connected in cascade, a cross-jumpering frame including a first terminal connected to a bank contact of said inder and other terminals corresponding in number of the full complement of stations on the called party line connected to contacts of the relays of said second set of relays, a further relay, a connection from said further relay to a wiper of said finder adaptedy to engage said bank contact, a jumper wire connected between said first terminal and each of said second terminals which corresponds to an out of service station on the party line, and circuits for said tuned relays including contacts of lthe relays of said second set and make contacts of said further relay whereby said further relay operates to complete the circuit of said tuned relays only for those `relays of said second set which correspond to out-ofservice stations of said party line.

6. An automatic telephone `switching system, according to claim 5, further comprising a uni-directional conducting device connected in each jumper wire.

7. An automatic telephone switching system, according to claim 5, further comprising a holding relay, a circuit for said holding relay adapted to be closed during interruptions ofsaid ringing currents, contacts for said holding relay, and locking circuits for the relays of said second set extending over said contacts.

8. In an automatic telephone switching system, party lines, means for extending connections to` said party lines, an intercept discriminator, switching means for extending a connection from a called party line to said discriminator when a call is Imade to a party line, means for applying ringing currents of different character to said party line, a rst set of relays in said discriminator adapted to respond selectively to said ringing currents of different character, and a second set of relays in said discriminator connected in cascade for operatively and successively connecting to said line only those of said first set of relays which corre-- spond to stations out of service.

9. In an automatic telephone switching system, party lines, means for extending connections to said party lines, an intercept discriminator, a nder switch for extending a connection from a called party line to said discriminator when a call is made to a party line, means for applying ringing currents of diierent frequency to said party line, a rst set of tuned relays in said discriminator adapted to respond selectively to said ringing currents of different frequency, means for connecting one terminal of said tuned relays to said line and a second set of relays in said discriminator connected in cascade for successively completing the circuits of only those of said first set of relays which correspond to stations out of service.

l0. In an automatic telephone switching system, party lines, means for extending connections to said party lines, an intercept `discriminator, a nder switch for extending a connection from acalled party line to said discriminator when a call is made to a party line, means for applying ringing currents of different frequency to said party line, a rst set of tuned relays in said discriminator adapted to respond selectively to said ringing currents of diierent frequency, means for connecting one terminal of said tuned relays to said line, a second set of relays in said t' discriminator connected in cascade, and means controlled by said finder and said second set of relays for completing 1n a sequential order the circuits of only those tuned relays which correspond to out of service stations.

1l. In an automatic telephone switching system, party lines, means for extending connections to said party lines, an intercept discriminator, a finder switch for extending a connection from a called party line to said discriminator when a call is made to a party line, means for applying ringing currents of different frequency to said party line, a first set of tuned relays in said discriminator adapted to respond selectively to said ringing currents of different frequency, means for connecting one terminal of said tuned relays to said line, a second set of relays in said discriminator connected in cascade, a further relay in said discriminator, circuits for said further relay including a wiper of said 'dnder switch and contacts of said second set of relays, and circuits for each of said tuned relays including make contacts of said further relay whereby said further relay operates to complete the circuit of said tuned relays only for those relays of said second set which correspond to out-of-service stations of said party line.

12. In an automatic telephone switching system, party lines, means for extending connections to said party lines, an intercept discriminator, a finder switch for extending a connection from a called party line to said discriminator when a call is made to a party line, means for applying ringing currents of different frequency alternatively to one or the other side of the party line, a irst set of tuned relays in said discriminator adapted to respond selectively to said ringing currents of different frequency, means for connecting one terminal of said tuned relays to that side of the line to which ringing current is applied, and a second set of relays in said kdiscriminator connected in cascade for completing in sequential order the circuits of only those of said tuned relays which correspond to out of service stations.

13. In an automatic telephone switching system having party4 lines and means for extending connections to said party lines, the combination comprising an intercept discriminator, a finder switch for extending a connection from a called party line to said discriminator when a call is made to said called party line, means for applying ringing currents of different frequency alternatively to one or the other side of said party line, a first set of tuned relays in said discriminator adapted to respond selectively to said ringing currents of diiferent frequency, means for connecting said tuned relays to that side of the line to which ringing current is applied, a second set of relays in said discriminator connected in cascade, a change-over relay comprising back, front and movable contacts and arranged to begoperated only when ringing currents are-applied to one particular side of the line, a cross-jumpering frame including a lirst terminal connected to a bank contact of said finder and other terminals corresponding 'in number to the full complement of stations on said called party line and connected alternatively to said back and front contacts, connections from said movable contacts to contacts of said second set of relays, a further relay, a connection from said further relay to a wiper of said finder adapted to engage said bank contact, a jumper wire connected between said first terminal and leach of said second terminals which corresponds to an References Cited in the file of this patent UNTTED STATES PATENTS 2,300,186 Wallace e Oct. 27, 1942 2,344,634 Powell Mar. 21, 1944 2,426,210 Hatton Aug. 26, 1947 

